Current methods for placing bone graft and other implants into the anterior spine—e.g., for Anterior Lumbar Interbody Fusion—are widely varied, and each method comes with its limitations.
U.S. Pat. No. 3,486,505 (Morrison) discloses an instrument to distract two closely adjacent vertebral bodies and at the same time insert an implant between the distracted vertebral bodies. The instrument acts as a protective guide and channel to the inserted implant and at the same time acts as a protective retractor to adjacent soft tissues.
US Published Patent Application No. US 2005/0165408 (Puno) discloses an instrument for inserting an implant in a space between adjacent bony portions including upper and lower guide members separated by a spreader with the implant positioned forwardly of the spreader. The spreader is movable forwardly between the guide members with a drive member to position the implant in a space between the bony portions. The spreader contacts the adjacent bony portions to facilitate withdrawal of the inserter instrument when the implant is positioned in the space.
US Published Patent Application US 2006/0195097 (Evans) discloses an apparatus for use with a spinal implant including a handle structure with a passage. A shaft with a screw thread is moveable within the passage in the handle structure. A pusher block is linked to the shaft, and has a forward surface configured to engage the spinal implant. A screw-threaded clutch member is supported on the handle structure for movement into and out of engagement with the screw thread on the shaft.
The DePuy Spine “Oz Inserter” and associated Pusher Blocks are described in the Technique Guide for the Universal ALIF Instrument Set. This Inserter Assembly is comprised of two long rigid blades (or ramps) that are pivotably connected at a (variable) distance apart. The distal blade tips can be placed into the disc space, while an inserter shaft can be advanced between the blades and towards the distal blade tips. A pusher block on the end of the inserter shaft can thereby advance the implant towards the blade tips and into the intervertebral body disc space. Advancing the inserter shaft and pusher block serves to spread the blades apart and to open the disc space for placement of the implant. The blades can also be used as a spreader by virtue of their pivot point, as the surgeon squeezes the blade handles to provide additional distraction of the disc space.
The DePuy Spine Keystone Blades are described in the Technique Guide for the Keystone Graft Instruments. There are two types of Keystone ramps (or blades) described, with the standard ramps consisting of flat metal blades that are flexibly connected at their proximal end. The blade tips are inserted into an intervertebral body disc space, and an implant can be pushed distally into the disc space by means of an inserter shaft which holds the graft. Impaction of the graft implant serves to spread the ramps apart as the implant is advanced into the disc space. There is also a Modular Insertion Ramp instrument, whereby the flat blades are assembled to an adjustable handle. The handle can be opened up to allow the graft to fit between the ramp blades. Again, the implant can be pushed distally towards the disc space by means of a pusher, while Impaction of the graft serves to spread the ramps apart. The ramps are them removed by rocking and pulling them out while leaving the implant in place.